The noun 帝国 (dìguó) means "empire," a large political territory ruled by an emperor. It is composed of 帝 (emperor) and 国 (country/state). It is used in both historical and modern contexts, such as 罗马帝国 (Roman Empire).
罗马帝国曾经是世界上最强大的国家之一。
Luómǎ Dìguó céngjīng shì shìjiè shàng zuì qiángdà de guójiā zhī yī.
The Roman Empire was once one of the most powerful countries in the world.
这个商业帝国是他白手起家建立的。
Zhège shāngyè dìguó shì tā báishǒuqǐjiā jiànlì de.
This commercial empire was built by him from scratch.
历史上很多帝国最终都走向了衰落。
Lìshǐ shàng hěn duō dìguó zuìzhōng dōu zǒuxiàng le shuāiluò.
Throughout history, many empires eventually declined.